Illumination

ABSTRACT

Illumination system utilizing H.I.D. (high intensity discharge) lamps, and having a subordinate lamp automatically activated to establish immediate illumination when the H.I.D. lamp circuit is turned on, i.e., without awaiting the usual warm-up period, and to maintain illumination during periods of voltage dip (which normally extinguishes H.I.D. lamps) in the circuit supplying them, as well as during subsequent recovery and restarting the H.I.D. lamps after extinguishment as a result of voltage dip or other outage condition.

United States Patent Price [4 1 Sept. 19, 1972 ILLUMINATION 3,517,254 6/ 1970 McNamara, Jr ..315/91 [72] Inventor: Lorenzo S. Price, Creve Coeur N10- 2,476,517 7/1949 THUS ..315/87 [73] Assignee: The Edwin F. Guth Company, St. primary Examin'e,- Nathan hf Lows Attorney-Paul M. Dcnk [22] Filed: Feb. 13, 1970 57 ABS CT [21] Appl. No.: 11,202 1 Illumination system utilizing H.l.D. (high intensity discharge) lamps, and having a subordinate lamp auto- [g] 38.51 ..315/91, 315/87 maficany activated to establishimmediate illumination [58] Flat.ld 39/10 when the HJSD lamp circuit i turned on, Le without l8 0 TC l /8 91, 88 awaiting the usual p p and to maintain lumination during periods of voltage dip (which nor- [56] Rem-ewes C'ted mally extinguishes H.I.D. lamps) in the circuit supply- UNITED STATES PATENTS ing them, as well as during subsequent recovery and restarting the RID. lamps after extinguishment as a 1,511,097 10/1924 Althoff et al ..315/87 X R f [ta th ta dfi 2,043,023 6/1936 Westerndorp ..315/91 0 v0 ge or 0 er ge I on 3,486,068 12/1969 1 Claim, 5 Drawing Figures Dunn et a]. ..315/87 P'A'TE'NTEDsEP 19 I912 VOLTS T\ME FlQ. 1

LQQENZO 5. Fame (9 MiJQ/i ILLUMINATION The invention relates to illumination, and particularly to a system which utilizes HID. (high intensity discharge) lamps, and to a fixture embodying such system.

H.l.D. lamps are being widely used in industrial and commercial lighting, as well as in street lighting, but they are possessed of certain characteristics which render them undesirable where instantaneous and continuous illumination is required. The source of illumination in such lamps is a translucent envelope charged with ionizable gas usually argon, and containing a modicum of metal or metal compound, such as mercury, sodium, or a metal halide, which is conductive when cold (i.e., in its liquid or solid state) but is vaporizable, in time, when a sufficient voltage is impressed across the electrodes at opposite ends of the translucent envelope. After energization of an H.I.D. lamp at the appropriate voltage, the time required for the contents of the envelope to begin to emit substantial light is noticeably long to persons accustomed to the instantaneity of incandescent light. The time lag varies with the materials employed, e.g., 2 minutes with sodium, 4 minutes with mercury, and up to minutes with the halides. Such slow starting breeds impatience and dissatisfaction with the lighting system.

Furthermore, H.I.D. lamps are prone to go out when the voltage with which they are energized dips to about 70 percent or less of normal root-mean-square value for a time period of micro-seconds (0.000030 of a second); and after they go out, there is a substantial delay, even if normal voltage is restored within a second, during which the vaporized cold-conductive material within the envelope must first cool to condense, and thereafter be reheated to vaporize before substantial light emission is resumed. As an antidote for such unexpected and unwanted periods of darkness, it has heretofore been proposed to provide areas normally illuminated by H.I.D. lamps with an independent incandescent lamp lighting system, which may be ac tivated to bring darkness into light while the H.I.D. illumination is in default. Such activation, even if accomplished by remote control, must, as a practical matter, be manually initiated, and hence requires not only time (sometimes more time than it takes for H.I.D. lamps to cool, recover, and relight), but groping in the dark to find the right switch to throw or button to press. It has also been proposed to provide, in the area to be illuminated by H.l.D. lamps, a photoelectric cell which is constructed and arranged to turn on the auxiliary incandescent lamp system after the cell senses darkness, but since the photoelectric cell cannot discern whether the light impinging upon it is emanating from an H.l.D. lamp or from an incandescent lamp, it will either not turn off the incandescent lamp system when the RID. system comes back on, or it will immediately turn oiT the incandescent system which it has just turned on, unless it is in some way shieled from light emanating from the incandescent sources, a condition which is difficult, if not impossible, to achieve if both the H .I.D. lamp and the auxiliary incandescent lamp are housed in the same reflector.

It is therefore an object of the present invention to provide an H.I.D. illumination system, and a lighting fixture involving the same, which will automatically turn on a subordinate incandescent lamp system during starting of the IUD. system, as well as when a voltage dip of magnitude such as to cause extinguishment of the HID. lighting system is sensed; and will automatically turn off the subordinate system when the IUD. system comes back on.

To accomplish the aforesaid object, the invention contemplates the provision of a subordinate system .for energizing one or more incandescent lamps (or other non-HID. lamps) from a source which may be, but is not necessarily, independent of the source which energizes the IUD. lamps in the system, except that activation and deactivation of the subordinate incandescent lamp system is controlled by the transitory voltage condition at the l-I.l.D. lamps. The subordinate system may, if desired, make use of one, both or none of the line conductors which supply energy to the H.I.D. lamp system. More specifically, the invention contemplates the provision, in an HID. lamp system, of a voltage sensing means connected between opposite legs of the supply line from which one or more H.I.D. lampsare energized. In particular, the voltage sensing means may be any instrumentality orcombination of instrumentalities which serve to keep the subordinate incandescent lamp system in open-circuit condition, as long as the voltage drop in the H.I.D. lamp or lamps is within the range required for the IUD. lamp to continuously emit light, but which operates to energize the subordinate incandescent lamp circuit when the voltage drop across the H.I.D. lamp or lamps departs: from the aforesaid range. Typical of the instrumentalities suitable for the purpose are relays, diodes, semi-conductors and combinations of the same. For example, two relays, each having a coil and a set of normally closed contacts, may be provided, with the coil in each relay separately connected across the legs of the IUD. lamp energizing circuit, and in parallel circuit relation with the lamp or lamps; the contacts of one relay being in series circuit relationship with the coil of the other relay, and the contacts of the other relay being in series circuit relationship with the lamp or lamps in the subordinate incandescent lamp circuit. Of course, the two relays may be embodied in the same apparatus as long as the contacts of one control the flow of current to the coil of the other. Alternatively, in substitution for the first-mentioned relay, an appropriate diode or semi-conductor may be inserted in place of the coil and contacts of the firstmentioned relay in series with the coil of the second-mentioned relay.

Given a system of the kind described in the preceding paragraph, a lighting fixture embodying thesame may typically comprise an H.I.D. lamp with appropriate receptacle, andan incandescent lamp with appropriate receptacle, both mounted within the same reflector located in a housing which also encloses the ballast (transformer and capacitor) commonly used for the energization of an H.I.D. lamp, together with the relays, or other instrumentalities provided for automatically energizing the incandescent lamp as and when a voltage condition, which causes the IUD. lamp to fail or cease to emit light, prevails even momentarily.

The accompanying drawings illustrate a typical embodiment of the invention in a lighting fixture, and diagrammatically illustrate the voltage conditions likely to occur in an H.l.D. lighting system which create the utility for the invention, as well as schematic illustrations of the circuitry involved in several embodiments.

In the drawings:

FIG. 1 is a representation of an oscillogram illustrating the conditions which may be expected to exist, on occasions, in an I-I.I.D. illuminating system, the existence of which conditions is sensed, in accordance with the invention, to activate the subordinate incandescent lamp system;

FIG. 2 is a diagrammatic view of a typical H.I.D. lamp circuit forming a part of the prior art;

FIG. 3 is a schematic diagram of one embodiment of the circuitry involved in a lighting system organized and arranged in accordance with the present invention;

FIG. 4 is a schematic diagram of the circuitry involved in a further embodiment of the invention but showing only one fixture; and

FIG. 5 is a vertical sectional view of a lighting fixture embodying the invention.

The oscillogram of FIG. 1 illustrates in full lines the voltage drop across an HID. lamp while current is flowing through it under various normal and abnormal conditionswhich may be expected to occur; and in broken lines the potential differing between opposite terminals of the I-I.I.D. lamp while voltage is available at, but no current is flowing through, the lamp. As mentioned previously, when an I-I.l.D. lamp is ,cold (i.e., below the temperature at which the cold-conductive metal or halide is vaporized), its electrical resistance is low (and hence when current flows through the lamp, the voltage drop within the lamp is low) and such starting conditions are illustrated in zone A of FIG. 1, where only a few cycles of voltage are plotted, but those skilled in the art will understand that hundreds occur during the warm-up period in which the coldconductive metal or halide is vaporized. With I-I.I.D. lamp wherein mercury is the cold-conductive element, the warm-up period A may be expected to endure for about four minutes before the mercury has vaporized, or the lamp emits measurable light. Once the cold-conductive element of the IUD. lamp has vaporized, the conductivity of the lamp decreases sharply, and the amplitude of the voltage wave shown at zone B of the oscillogram illustrates, vis-a-vis zone A, the relative magnitude of the voltage drop across the H.I.D. lamp during normal light emission. The duration of zone B is normally as long as the management desires light, but abnormalities do occur without advance notice, and, as hereinbefore mentioned, a supply voltage dip D to 70 percent of normal for a miniscule part of a second will not only extinguish the arc in an H.I.D. lamp, but render it temporarily non-conductive. When such occurs, the lamp must undergo a coolingofi" period C, during which no current can flow through it. The duration of the cooling-off" period depends not only upon ambient thermal conditions, but upon the time required for the vaporized cold-conductive element to recondense to its cold state of liquid or solid, and become sufficiently conductive to be revaporized. The cooling-off" period may endure for as much as twenty minutes after the occurrence of a voltage dip, or other momentary power outage. Regardless of the duration of the cooling-off period, once conductivity is restored, the lamp must go through a repetition of the initial warm-up period, represented in FIG. 1 as zone A, before restoration of normal light emission as represented by zone B in FIG. 1. Zones A, C and A are cross-hatched to connote darkness, in contrast with zones B and B' wherein the I-I. I.D. lamp is normally operating to emit light.

The circuitry for a conventional H.I.D. lamp system of the prior art is illustrated in FIG. 2 of the drawings, where an l-I.l.D. lamp 1 is energized from a remote source of power such as a generator 2, stepped up to transmission voltage by a transformer 3, and their, in reasonable proximity to the locus of the lighting system, stepped down from transmission voltage to distribution voltage by a transformer 4. From the secondary of transformer 4, a feeder conductor 5, through switch 50, supplies power to the H.I.D. lighting system, and perhaps other instrumentalities. The system for energizing a single I-I.I.D. lamp, such as 1, involves a ballast, usually in the form of an auto transformer 6, connected for energization between conductor 5 and a ground or neutral conductor 7. The auto transformer 6 has its secondary connected through conductor 8 to a capacitor 9, and from there through a conductor 10 to one side of H.I.D. lamp 1, the other side thereof being connected to ground or neutral conductor 7 in parallel circuit relationship with the primary of the auto transformer 6. As mentioned previously, conductor 5 may be connected to energize other I-I.I.D. lamps than 1 or other instrumentalities, as, for example, through branch conductors ll, 12, 13 and 14. The present invention utilizes all of the circuitry and instrumentalities illustrated in FIG. 2, but adds thereto the control instrumentalities necessary to sense the voltage condition in the circuitry of FIG. 2, which either will produce, or has just produced, a condition wherein the H.I.D. lamp is not emitting light, despite the fact that full voltage is available at it; and the above-mentioned control instrumentalities are of a character such that when they sense such conditions, they automatically complete a circuit to a subordinate lamp, such as an incandescent lamp, from a subordinate source of power, which may be wholly independent of the generator 2 (as, for example, a battery source or a stand-by generator), or may be supplied from generator 2 through a different distribution transformer than 4.

Turning now to FIG. 3 for an illustrative embodiment of the circuitry involved in the automatic activation and controlof the subordinate lighting system of the present invention, it will be observed that the whole of the circuitry shown in FIG. 2 is utilized, and the same reference characters designate corresponding elements thereof, but the circuitry commencing with the autotransformer 6 is duplicated to show a system embodying a plurality of I-I.I.D. lamps and subordinate incandescent lamps, in contrast with the single lamp system of FIG. 2.

Essentially, the circuitry and instrumentalities which FIG. 3 adds to that of FIG. 2, includes a subordinate source of electrical energy illustrated as a battery 15, one side of which is grounded, a conductor 16 extending from the battery 15 to a branch 17 which is permanently connected to contact 18 of a relay 19 having a coil 20, and also having an opposite contact 21 which is permanently connected, through a conductor 22, with one side of an incandescent lamp 23, the other side of which is permanently connected with the neutral or ground conductor 7 which also forms a part of the circuitry shown in FIG. 2. The coil 20 of relay 19 is connected in parallel circuit relation with H.I.D.

lamp 1, but the contacts 18 and 21 thereof are biased to a position whereat the circuit between contacts 18 and 21 is normally closed, but whenever coil 20 of the relay is energized to a voltage which is critical in the operation of the H.I.D. lamp 1, the circuit between contacts 18 and 21 is automatically opened. The aforesaid critical voltage is that which prevails when the H.I.D. lamp 1 is emitting normal light. The additional circuitry and instrumentalities also include a means for sensing another critical voltage condition at H.I.D. lamp 1, and is illustrated in FIG. 3 as a relay 24, whose contacts 25 and 26 are normally closed, but under an abnormal condition, are opened by the energization, at the lastmentioned critical voltage, of coil 27. The last-mentioned critical voltage condition occurs when the voltage at opposite terminals of the H.I.D. lamp exceeds the range which prevails while the H.I.D. lamp 1 is emitting normal light, as, for example, when the H.I.D. lamp is extinguished by the occurrence of a voltage dip, whereupon no current flows through the lamp, with the result that the potential difference between the lamp terminals substantially exceeds the voltage drop through the lamp while emitting normal light. In other words, when H.I.D. lamp 1, despite the availability of voltage at it, is not conductive, as during periods of cooling-off after a voltage dip, the voltage on coil 27 of relay 24 is higher than when the H.I.D. lamp is emitting normal light, and it is during such periods of inordinately high voltage on relay coil 27 that the circuit for energizing coil 20 of relay 19 is opened by the separation of contacts 25 and 26 of relay 24. When the contacts 25 and 26 are thus separated, the circuit from conductor through conductor 28 to coil 20 of relay 19 is interrupted, and contacts 18 and 21 close to complete a circuit to the incandescent lamp 23 from battery through conductors 16, 17, 22 and ground On the other hand, when H.I.D. lamp 1 is emitting normal light, the voltage on relay coil 27 is inadequate to interrupt the electrical connection between contacts 25 and 26, and thus coil of relay 19 is energized to maintain its contacts 18 and 21 separated. Those skilledv in the art will understand that the functions of the separate relays 19 and 24 may be accomplished by a single relay device having two coils and two pairs of contacts.

As mentioned previously, the embodiment shown in FIG. 3 involves a plurality of H.I.D. lamps in which the several instrumentalities above described are duplicated; and the duplicates are designated by a three-digit reference character whose last digit or two corresponds to the one or two digit reference numerals previously referred to, e.g., relay 106, capacitor 109, conductor 110, H.I.D. lamp 101, incandescent lamp 123, relay 124, relay 119 are, respectively, duplicates of the parts hereinbefore designated 6, 9, 10, 1, 23, 24, and 19.

As indicated hereinbefore, the relay 24 may be replaced by a diode, and FIG. 4 illustrates the circuitry of a system employing such, and utilizing the same reference characters as those shown in FIG. 3 for identical parts. In this embodiment, a diode 29 is con nected in series with coil 220 of relay 219. The diode is selected so as to become conductive in the direction from conductor 16 toward conductor 7 when the voltage drop across the H.I.D. lamp reaches the normal operating value, i.e., when the lamp is emitting light in the normal way; and the diode remains so conductive at voltages in excess of the normal operating value. While thus conductive, the diode permits current to flow from conductor 10 through coil 220 of relay 219 to thereby open the normally closed contacts 218 and 22] thereof, and thereby disconnect the incandescent lamp 223 from its source of power 15.. On the other hand, diode 29 is always conductive in the direction from conductor 7 toward conductor 10, but when: during starting the voltage drop across H.I.D. lamp 1 is substantially lower than the normal operating voltage drop thereacross; the current traversing coil 220 is insufficient toopen the normally closed contacts 218 and 221, and during cooling off, after a voltage dip which extinguishes H.I.D. lamp 1 (at which time that lamp is traversed by no current), no current can traverse coil 220 and consequently contacts 218 and 221 remain in their normally closed position at which'they connect incandescent lamp 23 to its source of power 15.

The invention also envisions a composite lighting fixture which includes the voltage sensing and control instrumentalities of the system illustrated by FIGS. 3 and 4. Such a fixture is shown in FIG. 5, where the circuitry and control instrumentalities correspond to the system schematically illustrated in FIG. 3. Such a fixture may comprise a housing 30, whose lower end is open and provided with a suitable lens 31, above which is mounted a suitable reflector 32. At the upper end of the housing, there is mounted in one corner an autotransformer corresponding to that of FIG. 3, and in the opposite corner, a capacitor 9 corresponding to that of FIG. 3. At top center. of the housing, a receptacle 33 is mounted to accommodate H.I.D. lamp 1, with its lightemitting surface disposed wholly within reflector 32, and its neck and base extending through a hole 34 in the crest ,of said reflector. Similarly, a receptacle 35 is mounted in the lower righthand corner of the housing 30 to accommodate an incandescent lamp 23, whose neck projects through a hole 36 in the reflector. At right center, there is mounted a composite relay 37 which, in a unitary housing,includes the counterparts of relays 19 and 24 of FIG. 3. Hence, the composite relay 37 has four contact terminals 38, 39, 40 and 41, which correspond, respectively, with contacts 26, 25, 18 and 21 of FIG. 3. The several conductors which interconnect the transformer 6, the capacitor 9, the coils of composite relay 37, the terminals of relay 37, the sockets 33 and 34, bear the same reference characters as the corresponding conductors in FIG. 3. It will be understood that the composite relay 37 may be replaced by the single relay 219 and diode 29, and the fixture wired in accordance with FIG. 4.

The number of the fixtures which may be energized from the same feeder 5 and the same subordinate source through the same conductor 16, in the manner shown in FIGS. 3 and 4, is limited only by the magnitude of the respective sources of power and the respective conductors. In fact, given a ballast (transformer 6, and capacitor 9) capable of simultaneously serving a plurality of H.I.D. lamps, one set of the voltage sensing and control instrumentalities, such as relays 19 and 24 or diode 29 and relay 219, is sufficient for a plurality of H.I.D. lamps and subordinate incandescent lamps connected in parallel circuit relation, respectively, across conductors 7 and 10, and across .conductors 7 and 16.

Those skilled in the art will understand that when the H.I.D. lamp 1 is emitting normal light (i.e., when current traverses the lamp as an arc), the voltage drop across it in a typical case may be 90 to 135 volts R.M.S., which is greater than the voltage drop (e.g., 10 to 50, volts R.M.S.) across the lamp when it is starting from cold (i.e., when current traverses the lamp by conduction through the cold-conductive element while in the liquid or solid state), but less than the potential difference (e.g., 220 volts R.M.S.) between opposite terminals of the lamp when the lamp is cooling off after a voltage dip has extinguished it (i.e., when, despite the availability of normal voltage at it, no current traverses the lamp) because the cold-conductive element is in the vapor state. Hence, in the embodiment of FIG. 3, the coil 27 of relay 24 may be calibrated to open its normally closed contacts 25-26 (thereby to de-energize coil 20 of relay 19 and release its contacts 18 and 21 to their normally closed position) when the potential difference between opposite terminals of the H.I.D. lamp 1 is substantially in excess (e.g., 220 volts) of the normal operating voltage drop (e.g., 90 to 135 volts) across the lamp; and under such conditions, the subordinate source of power is automatically connected with the incandescent lamp 23. Similarly, the coil of relay 19 is calibrated to open its normally closed contacts 18 and 21 whenever the voltage across its coil is equal to or greater (e.g., 90 volts) than the voltage drop across the H.l.D. lamp when it begins to emit normal light; and under such conditions, the subordinate. source of power 15 is automatically disconnected from the incandescent lamp 23.

Thus, it is apparent that when the switch 50 is closed, after having been open for a period sufficient to permit the H.I.D. amp 1 to cool enough that its cold-conductive element is condensed, the high conductivity of the lamp during starting produces such a low voltage drop across it that the relay coil 20 is insufficiently energized to enable it to open the normally closed contacts 18 and 21 thereof. Consequently, the incandescent lamp 23 is energized simultaneously with the closing of switch 50, and remains energized until the arc strikes in the H.I.D. lamp and the lamp begins to emit normal light. At that time, the voltage drop in the H.I.D. lamp attains a value such that coil 22 of relay 19 is sufficiently energized to pull open the normally closed contacts 18 and 21, and thereby disconnect the incandescent lamp 23 from the subordinate source 15. The latter condition normally continues until switch 50 is deliberately opened unless, in the meantime, there occurs a voltage dip of magnitude such as to extinguish the H.I.D. lamp, whereupon, in the cooling-off period, the potential difference between opposite terminals of the RID. lamp becomes the voltage across coil 27 of relay 24, thereby opening its normally closed contacts and 26, and de-energizing coil 20 of relay 19 so that its normally closed contacts assume the position whereat the incandescent lamp is energized from the subordinate source, as previously described.

While two embodiments of circuitry suitable for use in accordance with the present invention have been disclosed in detail, and variations thereof have been indicated in the foregoing description, it is to be understood that the invention is not limited to the details of those embodiments. On the contrary, it is recognized t at rsonso ordin skilli he will readil envisi on g ther variations ai n d mod ifi cati ehs of the cii cuitry and system without departing from the spirit of the invention, and accordingly, it is to be understood that the invention is not limited to the details of the foregoing disclosure.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

l. A lighting fixture and circuitry for an illuminating system comprising in combination: a reflector, a first receptacle for accommodating a high intensity discharge lamp having a light emitting surface disposed within said reflector, a second receptacle for accommodating a lamp of different type having a light emitting surface disposed within said reflector, said first receptacle and second receptacle being connected to a normal source of voltage supply and subordinate source of voltage supply respectively, a transformer having a primary winding connected to be energized by said normal source of supply, and a secondary winding connected to feed said high intensity discharge lamp, a capacitor intervening said secondary winding and said high intensity discharge lamp, a diode connected in parallel circuit relation with said high intensity discharge lamp, said diode being connected on the side of said capacitor remote from said secondary winding, and being normally disposed for conducting charge in a direction towards said capacitor, a first relay coil connected in parallel circuit relation with said high intensity discharge lamp, said coil being connected on the side of said capacitor remote from said secondary winding and being in series circuit relation with said diode, said diode designed for interrupting the flow of current to said relay coil when the voltage condition across said diode senses a voltage condition signifying extinguishment of said high intensity discharge lamp, said subordinate source of voltage supply being substantially independent of said normal source of voltage supply and connected to selectively energize said lamp of different type, normally closed relay contacts responsive to said relay coil controlling the flow of current between said subordinate source of supply and said lamp of different type, said relay contacts being normally closed to provide for conduct of charge from said subordinate source of voltage supply to said lamp of different type during initial ignition of said high intensity discharge lamp until it emits normal light, and said relay coil responsive to the voltage condition across said diode for opening said relay contacts when the voltage across said high intensity discharge lamp is within the range at which it emits normal light.

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1. A lighting fixture and circuitry for an illuminating system comprising in combination: a reflector, a first receptacle for accommodating a high intensity discharge lamp having a light emitting surface disposed within said reflector, a second receptacle for accommodating a lamp of different type having a light emitting surface disposed within said reflector, said first receptacle and second receptacle being connected to a normal source of voltage supply and subordinate source of voltage supply respectively, a transformer having a primary winding connected to be energized by said normal source of supply, and a secondary winding connected to feed said high intensity discharge lamp, a capacitor intervening said secondary winding and said high intensity discharge lamp, a diode connected in parallel circuit relation with said high intensity discharge lamp, said diode being connected on the side of said capacitor remote from said secondary winding, and being normally disposed for conducting charge in a direction towards said capacitor, a first relay coil connected in parallel circuit relation with said high intensity discharge lamp, said coil being connected on the side of said capacitor remote from said secondary winding and being in series circuit relation with said diode, said diode designed for interrupting the flow of current to said relay coil when the voltage condition across said diode senses a voltage condition signifying extinguishment of said high intensity discharge lamp, said subordinate source of voltage supply being substantially independent of said normal source of voltage supply and connected to selectively energize said lamp of different type, normally closed relay contacts responsive to said relay coil controlling the flow of current between said subordinate source of supply and said lamp of different type, said relay contacts being normally closed to provide for conduct of charge from said subordinate source of voltage supply to saiD lamp of different type during initial ignition of said high intensity discharge lamp until it emits normal light, and said relay coil responsive to the voltage condition across said diode for opening said relay contacts when the voltage across said high intensity discharge lamp is within the range at which it emits normal light. 